Abundance and Run Timing of Adult Pacific Salmon in Big Creek, Becharof National Wildlife Refuge, 2004 Alaska Fisheries Data Series Number 2005–12
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U.S. Fish & Wildlife Service Abundance and Run Timing of Adult Pacific Salmon in Big Creek, Becharof National Wildlife Refuge, 2004 Alaska Fisheries Data Series Number 2005–12 King Salmon Fish and Wildlife Field Office King Salmon, Alaska September 2005 The Alaska Region Fisheries Program of the U.S. Fish and Wildlife Service conducts fisheries monitoring and population assessment studies throughout many areas of Alaska. Dedicated professional staff located in Anchorage, Juneau, Fairbanks, Kenai, and King Salmon Fish and Wildlife Offices and the Anchorage Conservation Genetics Laboratory serve as the core of the Program’s fisheries management study efforts. Administrative and technical support is provided by staff in the Anchorage Regional Office. Our program works closely with the Alaska Department of Fish and Game and other partners to conserve and restore Alaska’s fish populations and aquatic habitats. Additional information about the Fisheries Program and work conducted by our field offices can be obtained at: http://alaska.fws.gov/fisheries/index.htm The Alaska Region Fisheries Program reports its study findings through two regional publication series. The Alaska Fisheries Data Series was established to provide timely dissemination of data to local managers and for inclusion in agency databases. The Alaska Fisheries Technical Reports publishes scientific findings from single and multi-year studies that have undergone more extensive peer review and statistical testing. Additionally, some study results are published in a variety of professional fisheries journals. Disclaimer: The use of trade names of commercial products in this report does not constitute endorsement or recommendation for use by the federal government. Alaska Fisheries Data Series Number 2005-12, September 2005 U.S. Fish and Wildlife Service Abundance and Run Timing of Adult Pacific Salmon in Big Creek, Becharof National Wildlife Refuge, 2004 Jeffry L. Anderson Abstract The King Salmon Fish and Wildlife Field Office operated a weir on Big Creek, Becharof National Wildlife Refuge, in 2004 to estimate Pacific salmon escapement. Salmon are an important Refuge resource, and accurate escapement estimates are needed to conserve these species. In 2004, 11,906 Chinook Oncorhynchus tshawytscha, 24,957 chum O. keta, 10,451 coho O. kisutch, 3,295 pink O. gorbuscha, and 189 sockeye O. nerka salmon passed the Big Creek weir. Chinook and chum salmon migrated past the weir from late June to early September with peaks during the second week of July for Chinook and mid August for chum salmon. Coho salmon first passed the weir in early August with peaks in late August, early and mid September. Age 1.3 Chinook, 0.3 chum, and 2.1 coho salmon were the dominant age classes. Fewer age 1.1 jack Chinook salmon were observed compared to previous years. The sex ratios of Chinook and chum salmon were approximately 1:1, while the coho salmon run was comprised mostly of males (72%). Introduction The Alaska National Interest Lands Conservation Act specifically mandates that fish populations and their habitats be conserved in their natural diversity within the Becharof National Wildlife Refuge (Refuge; USFWS 1994). The conservation of Chinook Oncorhynchus tshawytscha, chum O. keta, coho O. kisutch, pink O. gorbuscha, and sockeye O. nerka salmon stocks that are exploited in commercial, sport, and subsistence fisheries requires accurate monitoring of escapement. Big Creek, the largest tributary to the Naknek River, provides important spawning habitat for Chinook, chum, and coho salmon. The majority of adult salmon spawning in Big Creek likely occurs within Refuge boundaries. Therefore, it is necessary to determine current levels of escapement to ensure conservation of these Pacific salmon stocks originating from the Refuge. In addition, information on human use and dependence upon Refuge resources is becoming more important as competition and conflict develops between user groups for the same finite resources (USFWS 1994). Monitoring salmon escapement in Big Creek provides managers with stock status data that can be used to manage these fisheries. Management decisions based on this information will benefit commercial, subsistence, and sport users. Conflicts between Chinook salmon commercial, subsistence, and sport fishermen in the Naknek River drainage have increased in recent years due to an increase in competition for a limited resource. From 1994 to 1998, the average commercial harvest of Chinook salmon was 4,116 (42%), sport harvest averaged 3,710 (38%), and subsistence harvest averaged 2,009 (20%) (Dunaway and Sonnichsen 2001). From 1990 to 2000, the sport harvest of Chinook salmon in the Naknek River averaged 4,028, with a range from 2,927 in 2000 to 5,552 in 1997 (Walker et al. 2003). In an attempt to balance increasing harvest with escapement goals, the Alaska Department of Fish and Game (ADFG) has implemented seasonal commercial and sport fishing closures, as well as harvest and gear restrictions to protect Chinook salmon in the Naknek River drainage. The biological escapement goal for Chinook salmon in the Naknek drainage is 5,000 spawning adults as indexed by aerial surveys (Dunaway and Sonnichsen 2001). This goal is Author: Jeffry L. Anderson is a fishery biologist with the U.S. Fish and Wildlife Service. He can be contacted at King Salmon Fish & Wildlife Field Office, P.O. Box 277, King Salmon, AK 99613; or [email protected]. Alaska Fisheries Data Series Number 2005-12, September 2005 U.S. Fish and Wildlife Service based on index counts, and therefore represents a minimum estimate of total escapement. Chinook salmon returning to spawn in Big Creek represent a sizeable portion of the entire Naknek River escapement. From 1990 to 2002, Chinook salmon escapement in Big Creek has averaged 35% of the total escapement into the Naknek River drainage, ranging from 895 to 2,531 (Sands et al. 2003). Numbers of Chinook salmon counted past the Big Creek weir from 2000 to 2003 ranged from 649 to 10,063, although numbers were not complete counts in some years (Whitton 2003; Anderson et al. 2004). Coho salmon are also an important species targeted by sport fishermen in the Naknek River drainage, with an average sport harvest of 7,020 during 1990 to 2000 (range 3,253 to 10,276; Walker et al. 2003). Currently, the ADFG has not established a biological escapement goal or management objectives, and no monitoring program exists to assess spawning escapement or overall exploitation of coho salmon in the Naknek River drainage (Dunaway and Sonnichsen 2001). Declines seen in some coho salmon runs in the ADFG Southwest Management Area may be due to excessive harvest, but the lack of escapement data prevents managers from verifying this conclusion (Minard et al. 1998). The lack of escapement data has become a major concern, and without this information it is difficult to determine the health of coho salmon stocks and thus determine appropriate escapement and harvest goals. Coho salmon counts past the Big Creek weir from 2000 to 2003 ranged from 806 to 9,600, although counts were not complete in some years (Whitton 2003; Anderson et al. 2004). The ADFG does not have biological escapement goals or escapement monitoring for chum or pink salmon in the Naknek River drainage. Harvest in the commercial fishery is monitored, however, and 34,481 chum and 24 pink salmon were harvested in the Naknek River commercial fishery in 2003 (Morstad et al. 2004). The average sport harvest of pink salmon in the Naknek River from 1990 to 2000 was 4,897 (range 1,283 to 23,178), and the average chum salmon sport harvest was 374 (range 179 to 607; Walker et al. 2003). Chum salmon passage at the Big Creek weir ranged from 3,240 to 33,943, and pink salmon passage ranged from 15 to 873 during 2000 - 2003 (Whitton 2003; Anderson et al. 2004). In 2000, the King Salmon Fish and Wildlife Field Office (KSFO) initiated a multi year study on Big Creek to: 1. Enumerate escapement of Chinook, chum, coho, pink, and sockeye salmon in Big Creek from 15 June to 15 October; 2. Describe the run timing of Chinook, chum, coho, pink, and sockeye salmon through the weir; 3. Estimate the weekly age and sex composition of spawning Chinook, chum, and coho salmon in Big Creek, such that simultaneous 90% confidence intervals have a maximum width of 0.20; 4. Estimate the mean length of Chinook, chum, and coho salmon by sex and age; and 5. Characterize current public use on Big Creek and Becharof National Wildlife Refuge lands by conducting a general survey of boaters passing the weir. Whitton (2003) reports results of the project from 2000 to 2002; Anderson et al. (2004) reports project results from 2003. This report focuses on work accomplished in 2004. 2 Alaska Fisheries Data Series Number 2005-12, September 2005 U.S. Fish and Wildlife Service Study Area Big Creek originates in the mountains south of Brooks Lake in Katmai National Park and flows northwest about 60 km before joining the Naknek River, 6 km east of King Salmon, Alaska (Figure 1). The drainage is comprised of numerous tributaries, small lakes, and ponds and is almost entirely located within Refuge boundaries. Big Creek is a clear water stream that supports five species of Pacific salmon and spawning populations of rainbow trout O. mykiss, Dolly Varden Salvelinus malma, Arctic grayling Thymallus arcticus, and northern pike Esox lucius. Round whitefish Prosopium cylindraceum, longnose sucker Catostomus catostomus, and lamprey Lampetra spp. are also present in Big Creek. The weir site is 35 km upriver from the confluence of Big Creek and the Naknek River. This section of the stream is characterized by glides and riffles flowing over sand, gravel, and small cobble substrate. Willow Salix spp., birch Betula spp., and grasses dominate the riparian zone. Maximum discharge often occurs during spring breakup, but high discharge also occurs during periods of heavy rainfall between late July and October.